A Genetic Approach to the Geography of Hypertension : Examination of Na+-K+Cotransport in Ivory Coast Africans

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Abstract
Outward Na+-K+ cotransport in erythrocytes from essential hypertensive Caucasian subjects was found to be excessively low (Co ⊖) compared to normotensives (Co ⊖) carefully selected for their negative family history of hypertension. Since the frequency of essential hypertension varies widely among different populations and is particularly high in certain coloured peoples, we compared erythrocyte Na+-K+ cotransport in normotensive and hypertensive subjects in Paris (France) and in Abidjan (Ivory Coast) to see whether defective cotransport was related to high blood pressure in the African group as well. Of the 66 French unselected normotensives investigated, 26 (39 %) were Co ⊖ whereas 14 out of 18 Ivory Coast unselected normotensives (79 %) were Co ⊖. 64 (80 %) of the 80 essential hypertensives examined in France were Co ⊖, but the proportion of Co ⊖ subjects among the Ivory Coast hypertensives was even higher. In addition, both hypertensives and normotensives in the African groups often had undetectable outward Na+ effluxes, a rare finding in the French subjects. We suggest that the high incidence of abnormal Na+-K+ cotransport in the Ivory Coast series may reflect a genetic propensity to hypertension in this population, and that consequently, Na+-K+ erythrocyte cotransport measurements might prove useful in defining geographic variations in hypertension.